manifest inspect: support authentication

Previous tests have worked by pure chance since the client and server
ran on the same host; the server picked up the credentials created by
the client login.

Extend the gating tests and add a new integration test which is further
capable of exercising the remote code.

Note that fixing authentication support requires adding a new
`--authfile` CLi flag to `manifest inspect`.  This will at least allow
for passing an authfile to be bindings.  Username and password are not
yet supported.

Signed-off-by: Valentin Rothberg <vrothberg@redhat.com>

docs/source/markdown/options/authfile.md

@@ -1,5 +1,5 @@
 ####> This option file is used in:
-####>   podman auto update, build, container runlabel, create, image sign, kube play, login, logout, manifest add, manifest push, pull, push, run, search
+####>   podman auto update, build, container runlabel, create, image sign, kube play, login, logout, manifest add, manifest inspect, manifest push, pull, push, run, search
 ####> If file is edited, make sure the changes
 ####> are applicable to all of those.
 #### **--authfile**=*path*

docs/source/markdown/podman-manifest-inspect.1.md.in

@@ -15,6 +15,8 @@ A formatted JSON representation of the manifest list or image index.
 
 ## OPTIONS
 
+@@option authfile
+
 @@option tls-verify
 
 ## EXAMPLES